Three prior patents of major importance in this field are the following:
U.S. Pat. No. 4,019,359, issued Apr. 26, 1977 to the Steel Company of Canada, Limited; PA1 U.S. Pat. No. 4,005,830, issued Feb. 1, 1977 to the Steel Company of Canada, Limited; PA1 U.S. Pat. No. 4,306,438, issued Dec. 22, 1981 to the Steel Company of Canada, Limited.
Prior to the innovations represented by the above-three patents, the conventional method of rolling hot metal strip involved the heating of an ingot or slab to approximately 2300.degree. F. (for steel) and reducing it in thickness by rolling it through a series of rolling mill stands. Normally, the rolling sequence took place in two stages referred to as roughing and finishing.
In the roughing stage, the slab or ingot was normally rolled through one or more rolling mill stands in a series of passes until it was reduced in thickness to a transfer bar approximately one inch thick. The roughing mill stage would typically include one or more vertical edging mills.
Following the roughing operation, the transfer bar was transferred on table rolls to a continuous finishing mill train where it was further reduced to the desired gauge.
Certain problems were encountered in the above-described conventional method of rolling hot metal strip, particularly arising from the long length of time that it took the transfer bar to feed into the finishing mill train. In order to address these problems, the inventions represented by the three U.S. patents listed above were developed.
Essentially, these three patents relate to the construction and operation of a downcoiler (and improvements thereon), capable of wrapping a strip or transfer bar about itself into a coreless coil (i.e. a coil with an open central eye), in which the heat contained in the strip was largely retained and not allowed to dissipate away. The heat retention arose from the compact form assumed by the strip or transfer bar when coiled upon itself.
The improvement represented by U.S. Pat. No. 4,005,830 related to the combination of a downcoiler with means allowing the simultaneous uncoiling of a previously coiled strip and the coiling-up of a new strip. In order to accomplish this, U.S. Pat. No. 4,005,830 describes and claims the use of pivotally mounted transfer arms, one on either side of the coil, equipped with inwardly directed stub mandrels capable of entering the open eye of a coil and then swiveling through approximately 100.degree. in order to move the coil from a coiling location (directly downstream of the bend rollers) to an uncoiling location further downstream. one major advantage of this construction is that it allowed a coiled-up strip to begin uncoiling at the coiling location, and then be transferred to the uncoiling location while uncoiling is taking place, so that the uncoiling can be completed in the second location. Meanwhile, a new strip or transfer bar could begin coiling up at the coiling location.
While the method and apparatus set forth in U.S. Pat. No. 4,005,830 represented a marked improvement over previous approaches (and have met with considerable commercial success) there is still room for further improvement in order to address the following disadvantages of the prior system using transfer arms.
a) Because of the high temperature of the strip or slab when it is in the coiled condition, considerable heat loss takes place from the hot edges, radiating laterally away from the coil. Heat is also radiated from the hollow eye of the coil. Although the use of heat shielding was known at the time the invention set out in U.S. Pat. No. 4,005,830 was made, the arrangement of the various elements in that prior patent were such as to prevent the use of close-lying heat shields to substantially limit heat loss from the hot edges and the coil eye. More specifically, the presence of the transfer arms and the necessity that the transfer arms be capable of lateral movement parallel with the coil axis, prevented the positioning of heat shields where they would do the most good, namely directly adjacent the hot side edges of the coil.
b) Further, the necessity of physical contact between the stub mandrels and the inside convolution of the coil (in order to transfer the coil from the coiling to the uncoiling position) caused heat to be taken away from the coil. Because the coil was rotating during the transfer procedure, "cold spots" were largely eliminated, but an unavoidable heat loss did occur simply due to the contact.
c) A further difficulty with the prior development related to the crushing or crumpling of the tail end of the slab or strip just as the uncoiling is being completed. More specifically, the inner "wrap" of the coil is fairly tightly curved, and by the time the uncoiling procedure is completed the temperature of the inside wrap has dropped, thereby making it stiffer and more resistant to flattening out. In U.S. Pat. No. 4,005,830, the straightening or flattening of the final portion of the coiled strip or slab was achieved by leaving the stub mandrels in the open eye of the coil at the uncoiling position. However, it will be understood that, if the transfer arms and stub mandrels were removed in order to allow closely adjacent heat shielding, the problem of crushing or crumpling the stiff, curved tail end of the strip or slab would resurface.
There is no doubt that a significant advantage would accrue if one were able to dispense with the transfer arms while providing some modality by which the job of the transfer arms could be accomplished, one which did not interfere with the positioning of laterally adjacent heat shielding. If that could be accomplished, one would then have to address the problem of insuring that the tail end of an uncoiling transfer bar or strip could be flattened out in order to avoid crushing or crumpling of the final portion.
The above considerations are all addressed in the present invention.
Additional prior publications of interest are as follows: DE OS 2613459, laid open Oct. 13, 1977; DE 3743057, granted on Sep. 1, 1988; European Patent Application 0327855, published 16.08.89; European Patent Application 0327854, laid open 16.08.89; European Patent Application 0320846, published 21.06.89; European Patent Application 0309656, published 05,04.89; U.S. Pat. No. 4,829,656, issued May 16, 1989; U.S. Pat. No. 4,703,640, issued Nov. 3, 1987; U.S. Pat. No. 4,611,988, issued Sep. 16, 1986; U.S. Pat. No. 4,528,434, issued Jul. 9, 1985; U.S. Pat. No. 4,698,897, issued Oct. 13, 1987;